1. Field of the Invention
The present invention generally relates to improvements in underwater pelletizers and more particularly to the water box of an underwater pelletizer constructed of a two-piece assembly for improved access to the cutter hub.
2. Description of the Prior Art
Underwater pelletizers are well known and operate in conjunction with a die plate having multiple orifices through which molten polymer or other extrudable material is extruded from the inlet housing of an extruder into strands, with the orifices terminating at the die face of the die plate. The pelletizer includes a powered rotary cutter having a cutter hub mounted on a shaft with a plurality of blades supported from the cutter hub which move against the die face for shearing the extruded polymer strands into pellets as the polymer (or extrudate) is extruded beyond the die face. A water box having inlet and outlet pipes encloses the die face, cutter hub and blades to form a cutting chamber through which water flows to quench and rigidify the extruded polymer strands, thus enabling the cutting blades to better shear the extruded strands into pellets. The flow of water through the cutting chamber defined by the water box also conveys a slurry of the water and sheared pellets through the outlet pipe to a pellet dewaterer and/or a dryer. The above described underwater pelletizers are disclosed in related U.S. patents including U.S. Pat. Nos. 4,123,207, 4,251,198, 4,621,996, 4,728,276 and 5,059,103, 5,624,688, all owned by the assignee of this invention.
Previous water boxes for underwater pelletizers have been made of one piece construction. During the pelletization process, if the polymer or other extrudate strands extruded through the die plate are not properly sheared the polymer strands can “wrap up” around the rotating cutter hub and drive shaft in the water box, and even get into the inlet and outlet pipes. Should cutter hub wrap up occur it has been necessary to separate the water box from the die plate so that the water box can be cleaned. If the pelletizer cannot be rolled back from the die plate, access to the cutter hub is impaired, making cleaning of the water box difficult. As a result, some operators try to clean the water box by taking the cutter hub off from the die plate side of the water box or, worse yet, try to use a towmotor to pull the pelletizer back, damaging the equipment. Therefore, a need exists for a water box that allows easy access to the cutter hub in the event of cutter hub wrap up or other conditions requiring access to the cutter hub or interior of the water box.